Increasing frame rate without speeding up the cloth simulation
In Blender 2.78, the speed for a cloth simulation can be adjusted here (Physics tab for a cloth object):



I did a quick test with a flag running at 24 FPS (normal speed), then changed the FPS to 60 which caused the simulation to run at a higher speed (unrealistic). Changing the "Multiplier" to a lower value reduced the speed while keeping the 60 FPS. If you change the FPS from 24 to 60 (2.5x) you need to have a multiplier of 1/2.5 = 0.4.

It seems the "base factor" is 24.

See the 2.78 release notes for more details.